Surgical repair of tissue defects, such as tears in soft tissue and tears of the attachments of soft tissues to bone, are typically accomplished via techniques based upon suturing. A common post-surgical complication is a failure of the sutures to keep the healing surfaces in contact with one another. Common failure mechanisms include tearing of the soft tissue near the suture anchor points, failure of the sutures, and sliding of the healing surfaces relative to one another.
As an example, repair of tendon/ligament to bone is a difficult challenge in orthopedic surgery. For example, there are approximately 600,000 rotator cuff surgeries annually in the US alone. Surgical repair of the rotator cuff requires re-attachment of tendon to bone. However, attachment of dissimilar materials such as tendon and bone is mechanically challenging due to stress concentrations that arise at their interface. As a result, current approaches for rotator cuff repair are largely unsuccessful, with 20-94% failure rates. The two primary reasons for failed repair are: (1) poor initial mechanical fixation of the tendon and bone, and (2) a lack of regeneration of the native tendon-to-bone attachment structure. Similarly, re-attachment is a clinical challenge in other load-bearing tissues as well, including anterior cruciate ligament reconstruction, meniscus repair, and Achilles tendon repair.
To continue with the example of tendon to bone repair, the current standard of care for repairing a torn rotator cuff consists of grasping the tendon with suture and securing it to the bone using anchors. This results in load transfer from tendon to bone across the few anchor points and a high risk of failure at the tendon-suture or tendon-anchor interface. Furthermore, current care does not include any biologic augmentation at the repair site, and the typically poor healing at the tendon-bone interface is insufficient to mechanically integrate the tendon to the bone. A number of biologic grafts have been tested clinically for enhancing rotator cuff repair, but none have shown efficacy. Current grafts have been unsuccessful primarily due to their use as patches over the repair site (i.e., there are not interposed between the healing tendon and bone) and their poor mechanical properties.